1. Field of the Invention
The present invention relates to systems for separating particulates from fluids such as drain water and stormwater. Such particulates include particulates that float under most fluid movement conditions, particulates that do not float under most fluid movement conditions, and particulates that may be caught up in the fluid stream when the fluid is flowing, but that may otherwise float or be suspended within the fluid when the fluid is substantially stagnant. More particularly, the present invention relates to a separation system that may be independent, or form part, of a larger fluid transfer system.
2. Description of the Prior Art
Fluid transfer systems have been and will remain an important aspect of municipal services and commercial facilities management. The protection of ground water and natural bodies of water requires systems for diverting and/or treating water that contacts roadways, parking lots, and other man made structures. If such diversion or treatment systems are not provided, particulates and contaminants located on or forming part of such structures may be carried by drain water or stormwater to the natural water bodies and contaminate them. Local, state and federal laws and rules require municipalities, businesses and, in some instances, private entities, to establish means to reduce particulate and contaminant levels permissibly transferred to natural bodies of water from property under their control. Particular requirements may vary from jurisdiction to jurisdiction, but all are likely to become more, rather than less, stringent.
Previously, municipal water transfer and treatment facilities provided the only mechanism for diverting contaminated water away from natural bodies of water, either for holding or treatment for subsequent transfer to natural settings. In general, that process involved, and continues to involve, the establishment of a system of drains, such as in a parking lot or at a street curb, by which water enters a system of pipe conduits. Eventually, the water received from the drains reaches either a final outlet destination or is directed to a treatment system for contaminant removal. For purposes of the description of the present invention, “contaminated water” is to be understood to mean any water including floating particulates, such as Styrofoam™ containers and oil, for example; non-floating particulates, such as sand and silt, for example; and entrained contaminants, such as dissolved nutrients or metals, for example.
Land development produces increased levels of drain water and stormwater runoff, resulting in increased strain on existing water transfer and treatment infrastructure and an increased likelihood of natural water contamination. In an effort to reduce the impact of development on natural resources and municipal services, initial upstream fluid treatment has become a requirement in many land development, restoration and repair projects. That is, requirements in various forms have been established to ensure that before contaminated water enters the municipal water transfer and/or treatment system, it must be treated in a manner that reduces the level of contaminants entering the municipal system. Therefore, most new land development plans and upgrades to existing paved surfaces involve the insertion of a preliminary separation system, generally for connection to the municipal water-handling infrastructure.
Any preliminary separation system must be designed with the capability to receive fluid flowing in at a wide range of rates. For example, a mild rainfall resulting in rain accumulation of less than 0.25 inches over a span of 24 hours produces a relatively low flow rate through the system. On the other hand, for example, a torrential rainfall resulting in rain accumulation of more than two inches over a span of three hours produces relatively high flow rates through the system. It is desirable, then, to have a separation system capable of handling variable fluid flow rates with reduced likelihood of backup and flooding of the surface above. It is also desirable to control the flow through the system such that trapped particulates are not scoured or washed out of the device and re-entrained during high flows for passage downstream.
In addition to having a reasonable fluid flow throughput capacity, the separation system must be capable of performing the separation function for which it is intended. Specifically, it may be required to remove from the fluid flow path a certain number, type, or size of particulates. For example, some California municipalities require the removal of any particulates with dimensions greater than five millimeters. It would be preferable to have such a separation system that can remove from the fluid flow path the particulates for which it is designed at the widest range of flow rates but without causing backup or scouring/washout. For that reason, some such systems are designed with a bypass mechanism to permit direct flow through of fluid without preliminary treatment when relatively high flow rates are reached. Unfortunately, ineffectively designed separation systems fail to provide the best particulate removal and further fail to do so under flow rates that may not be particularly high.
There is an increasing need and requirement for separation systems associated with drain water and stormwater introduction to municipal water handling systems. However, it is important that they not be prohibitively expensive in order to ensure that meeting those needs and requirements is feasible. It is also of importance that such separation systems are relatively easy to access for maintenance. It is also preferable that separation systems provide a reasonable arrangement for storing accumulated particulates to minimize the possibility of clogged inlets and outlets and to extend the required maintenance cycle. Inline treatment systems of relatively modest size are particularly desirable for incorporating into existing fluid transfer systems, however, they may be prone to shorter maintenance cycles as a result of competing goals of reduced size, exit blockage minimization, and flow through capacity requirements.
Therefore, what is needed is a separation system that may or may not be part of a larger fluid handling system that is effective in accommodating varied fluid flow rates. What is also needed is such a separation system that conforms or substantially conforms with established particulate removal requirements. Further, what is needed is such a separation system that is configured to minimize clogging possibilities and to maximize particulate removal capability in a cost effective arrangement. Yet further, what is needed is such a separation system that includes means to minimize exit blockage under anticipated fluid flow conditions without compromising separation capability.